Chainmail

Chainmail is intended to be a sendmail replacement for
workstations. It is written in perl.

Included are an RFC 822 parser (the most complete perl
implementation AFAIK), a mail queuing system, an ESMTP client and
Net::DNS by Michael Fuhr.

At the moment, there are only per-user mail queues. In the
future, chainmail should be made trustworthy enough to be setgid
mail and deliver messages to a central shared queue. At the moment
the problem with this is that a cunningly created queue file could
quite possibly make chainmail eat CPU forever. In other words,
chainmail has not been audited for denial of service or other
security vulnerabilities, so it should not be run by (for example)
a cron script or with elevated privileges.